Hitherto, magnesium chloride and magnesium alkoxides have been widely used as a support material without being milled in the field of catalysts for olefin polymerization, specifically the homopolymerization or copolymerization of ethylene, propylene or the like. This may improve the catalyst activity and the morphology of polymer powder.
For example, for improving an obtained polymer in the morphology including a particle size, form, etc., a method in which a magnesium compound is supported on an inorganic oxide such as silica (for instance, see JP-A-S63-280707), or a method in which a magnesium compound is once dissolved in a solvent such as an alcohol and then precipitate again, which precipitate is used (for instance, see JP-A-S58-000811) is known.
However, these methods include very complicated steps, since they require the procedures of supporting, dissolving and precipitating a magnesium compound. Further, these methods have a defect that the catalyst is poor in stability of performance.
To use as a support of catalysts a magnesium compound obtained by reacting metal magnesium, an alcohol such as ethanol and a certain amount of halogen (for instance, see JP-A-H4-130107) is disclosed. However, the form (surface smoothness) of the polymer powder may not be satisfactory dependently on the polymerization conditions of this method.
A method in which metal magnesium and ethanol are reacted without solvent in the presence of iodine, followed by maintaining the reaction product for a few hours under reflux of an alcohol to prepare a catalyst is disclosed (for instance, see JP-A-H3-074341). However, by this method, the smoothness of the support to be obtained is not satisfactory.
A magnesium compound which is obtained by reacting metal magnesium and ethanol in the presence of iodine and which satisfies the sphericity S<1.60 and the particle size distribution index P<5.0 is disclosed (for instance, see JP-A-H4-370104). However, although the support is excellent in the sphericity and particle size distribution, when catalyst components are supported on the support and polymerization is carried out, resultant powder particles sometimes fracture.
A magnesium compound having the sphericity S<4.0, which is obtained by reacting metal magnesium, ethanol and iodine, is disclosed (for instance, see WO03/099749). However, although the magnesium compound has narrow particle size distribution and small sphericity, usable raw material magnesium is strictly limited.
A propylene-based random copolymer obtained by copolymerizing propylene and the other α-olefins has impact resistance and transparency superior to a propylene homopolymer, further has relatively low melting point so that it is excellent in low temperature heat sealing property. Therefore, the propylene-based random copolymer has been widely used for uses mainly including the field of packaging material such as various types of films.
As propylene-based random copolymers, for example, a random copolymer of propylene and ethylene, a random copolymer of propylene and an α-olefin having at least 4 carbon atoms, and a ternary random copolymer of propylene, ethylene and an α-olefin having at least 4 carbon atoms are known.
As to the above-mentioned propylene-based random copolymer, the larger the ratio of monomer copolymerized with propylene is, the more the melting point can be lowered, and it has been known that the impact resistance and low temperature heat sealing property are improved. On the other hand, as the composition ratio of the copolymerizable monomer increases, the amount of low molecular weight amorphous components having tacky nature increases, the amount of tackiness components at the time of forming a film increases and the blocking resistance tends to deteriorate. As the result, there are inadequacies that the commercial value is sometimes reduced and its use is limited dependently on the use.
Further, for producing a propylene-based random copolymer, a catalyst for olefin polymerization consisting of a solid titanium catalyst component, an organic aluminum compound and, if necessary an electron donating compound has been widely used (for instance, JP-A-H9-025316, JP-A-H9-059321, JP-A-H9-067416 and JP-A-H10-287710). However, in the case of producing it using a hydrocarbon solvent or propylene as a medium, there sometimes has problems that copolymer particles adhere to each other because of increase of the amount of the by-product low molecular weight amorphous components, that the productivity decreases because of increase of the viscosity of the polymerization system, and that in some cases, serious troubles occur in the production.
When the production is carried out by gas phase polymerization, in addition to increase of low molecular weight amorphous components and decrease of the melting point, the particles tend to melt by the enlarged heat of reaction involved with increase of the reaction rate, the copolymerization particles adhere to each other or fused to form agglomerates, and the particles tend to adhere to the inside of a reaction vessel. As the result, troubles are sometimes taken place such that block up or the like tends to occur when the powder is taken out from a polymerization vessel, productivity decreases or that the polymerization has to be terminated in the worst case.
On the other hand, a propylene-based block copolymer, for example, a propylene-based block copolymer consisting of a crystalline propylene copolymer part and an amorphous propylene-ethylene copolymer part (rubber part) has properties of high stiffness and excellent low temperature impact resistance, therefore, it is widely used for automobile parts, home electric appliance parts, foods field and other fields as well as general injection molding.
The propylene-based block copolymer having a high content of the rubber part exhibits excellent low temperature impact resistance, therefore, in the automobile parts field, a propylene-based block copolymer having a higher ratio of the rubber part is desired. However, since it is difficult to produce such a propylene-based block copolymer, for improving impact resistance, the method has been employed that an olefin-based elastomer such as an ethylene-propylene rubber, or a styrene-based elastomer is blended to a propylene-based block copolymer.
A propylene-based block copolymer is generally produced by homopolymerization of propylene or copolymerization of propylene with a small amount of the other α-olefin in the first process, followed by copolymerization of propylene with ethylene and/or the other α-olefin to prepare a rubber part in the second process.
The second process is frequently carried out by gas phase reaction, however, the rubber part has adhesiveness, in the production of a block copolymer, tackiness of the propylene-based block copolymer increases, and there are problems that powder particles agglutinate involved with deterioration of flowability in a polymerization vessel, and that troubles in the production tend to occur such as adhesion in the polymerization vessel and the like.
To contemplate increasing the amount of the rubber part, the above-mentioned problems get serious, and troubles such that the polymerization has to be terminated and the like are sometimes caused. Thus, the ratio of the rubber part in the production of a propylene-based block copolymer is limited under the existing circumstance.
As to the technique in order to produce propylene-based block copolymer particles containing a large amount of the rubber part, some approaches have been made.
For instance, JP-A-H9-506319 discloses a method that a crystalline polypropylene part is produced using a solid titanium catalyst component consisting magnesium, titanium and a halogen as the essential components in the first polymerization process, and an amorphous propylene-ethylene copolymer part is produced using a so-called Metallocene in the second polymerization process.
However, in this method, a step to inactivate the catalyst has to be provided after the first polymerization process, there having a defect that the processes complexity.
JP-A-2002-030128 discloses a method using a catalyst for olefin polymerization, which contains magnesium, titanium, a halogen, an electron donating compound and aluminum as the catalyst components.
However, this method cannot be said a sufficient technique to solve the problems in the production of the propylene-based block copolymer, since the technique of the solid catalyst used in this method is one similar to those of catalysts such as methods that a magnesium compound is supported on a porous inorganic oxide such as silica which is known technique (for instance, see JP-A-S63-280707), that a magnesium compound is once dissolved in a solvent such as alcohols, followed by precipitation again to obtain a catalyst (for instance, see JP-A-S58-811), and that a magnesium alkoxide compound which is obtained by reacting metal magnesium and an alcohol such as ethanol is used as a support (for instance, see JP-A-H4-130107).
From the above-mentioned back ground, a method is desired that can provide propylene-based block copolymer particles which have excellent particle flow property, from which molded articles excellent in stiffness and impact resistance can be prepared, and which can be produced with light load.
In view of the above-mentioned problems, a purpose of the present invention is to provide a magnesium compound which exhibits high activity without decrease of performances such as stereoregularity and can give an olefin polymer excellent in powder flowability and a method of production thereof, a solid catalyst component for olefin polymerization, and a catalyst for olefin polymerization.
Further, in view of the above-mentioned problems, a purpose of the present invention is to provide a propylene-based random copolymer having less tacky component, which can give a film excellent in low temperature heat sealing property and impact resistance, and a method that can stably produce the propylene-based random copolymer.
Furthermore, in view of the above-mentioned problems, a purpose of the present invention is to provide a propylene-based block copolymer having excellent particle flow property and a method of producing the same.